To "call an audible" is when you are on a date, or trying to pick someone up at a bar and the other party is not interested in you. The uninterested party will then "call an audible" on you by working in an interjection / rejection into their dialog in order to possibly soften the blow of rejection. This will allow them to state their judgement on you, or their actual position without them outright explaining to you that you need to back off.

(after a date, a buddy is talking to his friends and describes a meet up at a bar as follows):

Man 1: I met this girl at the bar, we had a few drinks, had a few laughs and just when I thought things were going well she totally called an audible (call an audible) on me!

Man 2: What?! That is messed up. How'd she do it?

Man 1: We were talking about different beers we liked and she said "Oh yeah my boyfriend and I love Hefeweizen"

To decide what to do at the last second after seeing all possible options and obstacles that come up.
Comes from football, seen when the quarterback goes up to the line of scrimmage, sees a defensive alignment he wasn't expecting, and adjusts by yelling out a new play.

I'm thinking of going jogging but if it rains I'll have to call an audible and go to the gym instead.